<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      body {
        margin: 0;
      }
      .container {
        width: 808px;
        height: 808px;
        margin: 50px auto;
        border: 1px solid;
        display: flex;
        flex-flow: row wrap;
      }
      .container > .box {
        width: 200px;
        height: 200px;
        border: 1px solid;
      }
      .box1 div {
        width: 50%;
        height: 50%;
      }
      .box1 {
        display: flex;
        flex-flow: row wrap;
      }
      .box1-1 {
        background-color: aqua;
      }
      .box1-2 {
        background-color: blueviolet;
      }
      .box1-3 {
        background-color: chocolate;
      }
      .box1-4 {
        background-color: darkkhaki;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div class="box box1">
        <div class="box1-1"></div>
        <div class="box1-2"></div>
        <div class="box1-3"></div>
        <div class="box1-4"></div>
      </div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
      <div class="box"></div>
    </div>
  </body>
</html>
